A human vertebra has a rearwardly projecting portion known as a spinous process. Bending of the spine can cause the spinous processes of adjacent vertebrae to move toward each other. This may, in some people, constrict the space in the spinal canal and foramina and, thus, may cause pain. Such constriction, which is known as stenosis, can be treated by the implantation of an interspinous spacer into the space between adjacent spinous processes.
Current interspinous spacers are typically constructed of separate pieces which require insertion from opposite sides of the spine, in a posterior approach, and necessitate rather large incisions, cutting both left and right thoracolumbar fascia as well as stripping the multifidus muscles from their attachments.
It is desirable to provide an interspinous spacer for implantation between spinous processes of adjacent vertebrae which can be laterally inserted in a first configuration through a single opening in a minimally invasive approach and which may then be deployed to a second configuration to maintain the spacer in position between the adjacent spinous processes.